Multifunctional restorative dental materials: Remineralization and antibacterial effect

Abstract

Remineralizing biomaterials have been a long-time pursuit in dentistry as a strategy to prevent or at least postpone the development of caries lesions around existing restorations, fissure sealants, and orthodontic brackets. Glass-ionomer cements, with a track record spanning four decades, have shown good results in situ. However, their low mechanical properties and bond strength to the tooth structure are limiting factors in several clinical situations. In the last decade, calcium orthophosphates (e.g., amorphous calcium phosphate/ACP), bioactive glasses (e.g., 45S5), and calcium silicates (e.g., mineral trioxide aggregate/MTA) have been tested as ion-releasing fillers in dentin bonding systems and resin composites. In vitro testing showed unequivocal evidences of hybrid layer remineralization, which reduces permeability and collagen degradation, therefore contributing to the longevity of bonded interfaces. On enamel, composites containing calcium orthophosphates were shown to promote mineral recovery in vitro and reduce mineral loss in situ. Besides fostering remineralization, some of these particles may also grant antimicrobial activity to resin-based materials, making them "multifunctional restorative materials." Studies show that bioactive glasses are effective against some bacterial species due to their alkalinity and effect on osmotic gradient. For calcium silicates, however, there seems to be no consensus among authors regarding antimicrobial effect, while calcium orthophosphates and glass-ionomers show no evidence of intrinsic antimicrobial activity.